Lubricating compositions



United States Patent 2,994,662 LUBRICATING COMPOSITIONS George M. Calhoun, Berkeley, and William A. Hewett, Oakland, Calif., assignors to Shell Oil Company, a corporation of Delaware No Drawing. Filed Dec. 2, 1957, Ser. No. 699,919

1 18 Claims. (Cl. 25248.6)

This invention relates to lubricants, particularly those useful for lubrication under severe operating conditions, such as under extreme high speed and at high temperatures.

It is well known that the high pressure occurring in certain types of gears and bearings may cause rupture of lubricant films with consequent damage to the machinery. It is known that various base lubricants can be improved in their protective properties for rubbing surfaces by the addition of certain substances, so-called extreme pressure agents, so that excessive wear, smiling and seizure which normally follow a break in the film lubricant are minimized or prevented.

It is known that certain compounds of metal-reactive elements, such as certain compounds of chlorine, sulfur and phosphorus, as well as certain other compounds, such as somecompounds of lead, impart extreme pressure properties to various lubricants. Notable among the substances heretofore used are the lead soaps, phosphoric acid esters, free or bound sulfur and certain chlorinated organic compounds. A principal objection to many of these extreme pressure agents is their generally high reactivity with the metallic surface, causing etching, 'corrosion and discoloration of the metal surface. Another objection to chemically reactive extreme pressure agents is that they alter the original chemical nature of the contacting surface, which under certain conditions is undesirable. Additionally, because of the activity of agents of this type, they usually are depleted rapidly resulting in only a temporary solution to the problem of extreme pressure lubrication.

It has now been discovered that improved extreme pressure lubricants are provided by a suitable lubricating oil containing certain essentially oil-soluble sulfur-containing carboxylic acids having the formula wherein R is an oil-solubilizing hydrocarbyl radical, preferably a C C alkyl radical, R is hydrogen or a short alkyl radical of from 1 to 4 carbon atoms, Y is an oxygen-containing radical such as -COOX, OH, etc., preferably COOH or OH, X is hydrogen or a hydrocarbyl radical, m is an integer of at least 7 and n is an integer of from 1 to 4, preferably Land at least one of the Y groups or -COOR' carboalkoxy being a carboxylic acid or carboxy (-COOH) radical.

Compounds of the type represented by the above formula can be prepared by reacting a mercapto acid or ester with an unsaturated acid or other equivalent compound. The mercapto acid or ester has the formula HSR"COOR' wherein R" is an .alkylene radical of not more than 4 carbon atoms, e.g. mercaptoacetic acid, alphaand betamercaptopropionic acid, .alpha-, betaand gamma-mercaptobutyric acid and O-mercaptovaleric acid, methyl or ethyl mercapto acetate, propionat'e or butyrate. The unsaturated long-chain acidic compound may be a longchain unsaturated fatty acid, e.g. oleic acid, linoleic acid, linolenic acid, erucic acid, ricinoleic acid or an unsaturated fatty alcohol, e.g. oleyl alcohol, 'ricinoleyl alcohol, *etc. Instead of the free acids or alcohols these compounds can be used in the form of their esters, e.g. methyl or ethyl oleate, lauryl oleate, glycerol trioleate or the like.

The additives used in oil compositions of this invention can be prepared by the methods described by Koenig et al., IACS 79, 362 (1957), or Fitzgerald, Jr., Org. Chem. 22, 197 (1957), or by any other suitable means and preferably at low temperatures (from room temperature to about 50 C.) and in the presence of a free radical catalyst such as =azo or peroxide catalysts or ultra-violet light and a non-reactive solvent such as benzene, toluene, xylene, or the like. Suitable initiators include various free radicalyielding initiators, for example, various organic peroxides,

such as aliphatic, aromatic, heterocyclic and alicyclic peroxides, such as diethyl peroxide, tertiary butyl hydroperoxide, dibenzoyl peroxide, ditertbutyl peroxide, dimethylthienyl peroxide, dicyclohexyl peroxide, dilauroyl peroxide and urea peroxide. These are mentioned by way of non-limiting examples of suitable organic peroxides. Other initiating compounds known include emulsion redox systems, such as a mixture of sodium bisulfite and persulfate, ammonium persulfate, alkali metal perborates, azo compounds, such as alpha,alpha-azodiisobutyronitrile, etc.

The following examples illustrate the preparation of suitable additives for use in oil compositions in accordance with the present invention.

EXAMPLE I About 600 grams of oleic acid and 223.5 grams of mercapto-acetic acid were mixed in a flask at 20-25" C. About 240 drops (30 drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 37 C. The reaction mixture was diluted with 2 volumes of diethyl ether, washed with 12 liters of water to pH 4, dried over Na SO filtered and the solvent stripped at 155 C. and 2 mm. pressure. The final product was a mixture of 9- and 10-carboxymethylmercaptostearic acid and analysis of the product was as follows:

About 600 grams of ethyl oleate and 223.5 grams of mercaptoacetic acid were mixed in a flask at 20-25 C. About 240 (30 drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 37 C. The reaction mixture was diluted with 2 volumes of diethyl ether, washed with 12 liters of water to pH 4, dried over Na SO filtered and the solvent stripped at 155 C. and 2 mm. pressure. The final product was a mixture of ethyl 9- and 10-carboxymethylmercaptostearate and analysis of the product was as follows:

Percent Percent Percent Percent Eq. Wt.

Found 65. 7 10. 5 16.0 7. 472 Theory 65. 6 10.51 15.9 7.96 402 EXAMPLE III with 12 liters of water to pH 4, dried over Na SO filtered and the solvent stripped at 155 C. and 2 mm. presure. The final product was a mixture of 9- and 10-carboxymethylmercap-to-l2-hydroxystearic acid and the equivalent weight of the product was found to be 207 (theory 195).

' EXAMPLE IV About 600 grams of glyceryl trioleate and 223.5 grams of mercaptoacetic acid were mixed in a flask at -25 C. About 240 drops drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 37 C. The reaction mixture was diluted with 2 volumes of diethyl ether, washed with 12 liters of water to pH 4, dried over Na SO filtered and the solvent stripped at 155 C. and 2 mm. pressure. The final product was a mixture of glyceryl tris(9- and 10-carboxymethylmercaptostearate) and the equivalent weight of the product was found to be 445 (theory EXAMPLE V About 600 grams of oleyl alcohol and 223.5 grams of mercaptoacetic acid were mixed in a flask at 20-25 C. About 240 drops (30 drops at a time) of t-butyl hydro- .peroxide were'added over a period of 2 hours and the temperature was kept at about 37 C. The reaction '{mixture was diluted with 2 volumes of diethyl ether,

washed 'with ,12. liters of water to pH 4, dried over Na SO filtered and the solvent stripped at 155 C. and 2 mm. pressure. The final product was a mixture of 9- and lO-carboxymethylmercaptostearyl alcohol. a The 'mercapto-modified acids or alcohols in general are oil-soluble and can be used in amounts of from about 0.5% to about 20%, preferably fromabout 1% to about 5% by weight. Although these mercapto-modified j acids or alcohols are oil-soluble some of them form opaque solutions which can be overcome and the solutions rendered transparent by addition to oils containing 'these mercapto products a small amount (01-10%) of an oil-soluble branched-chain aliphatic monohydric alcohol, oil-soluble high molecular weight fatty acid or monoester of said fatty acid and polyhydr'ic alcohols. The alcohols, fatty acids or monoesters can elfectively clarify oils containing mercapto acids or alcohols or derivatives thereof as described without destroying the extreme pressure properties of such oil compositions. The oil-soluble alkanols particularlyuseful as clarifiers are the so-called 0x0 alcohols derived from branched-chain olefins, such as polymers of lower alkenes Table 1 Alcohol Percent, wt.

3, 5-dlmethyl hexanol 4,5-dlmethyl hPxannl 3,4-dimethyl hexanol E-methyl heptanol 8-methyl heptanol Methyl hexannl 5,5-dimethy1 h Pxan nl alpha-alkyl alkan nls Others Other examples of suitable alkanols include 6-methyl-1- heptanol, 2-n-propyl-1-pentanol, 3-n-propyl-l-hexanol, -2,2-dimethyl-1-octanol, 10,10-dimethyl-1-undecanol, 3- isopropyl1-heptanol and mixtures thereof.

The fatty acids useful as clarifiers include the saturated 4 to 30 carbon atoms such as capric, lauric, oleic, linoleic, ricinoleic acids and mixtures thereof.

The monoesters derived from simple alkane polyols and long chain fatty acids useful as clarifiers include oil-soluble glycerol monooleate, glycerol monostearate, glycerol monoricinoleate, pentaerythritol monoand dilaurate, pentaerythritol monoand dioleate, pentaerythritol monoand distearate, mono, di-, and triethylene glycol monooleate, propylene glycol monoricinoleate, triethylene glycol monostearate, sorbitol monolaurate, mannitol monooleate, mannitol dioleate, sorbitol dioleate, etc.

The lubricating oils used in compositions of this invention can be a variety of synthetic or natural hydrocarbon oils having a viscosity-range of from 50 SUS at 100 F. to 250 SUS at 210 F. (SAE viscosity number ranging from SAE 5 to SAE The natural hydrocarbon oils can be obtained from paraflinic, naphthenic, asphaltic or mixed base crudes, and/or mixtures thereof. Synthetic oils include polymerized olefins, alkylated aromatics, isomerized waxes, copolymers of alkylene glycols and alkylene .oxide (Ucon fluids) which are described in US. Patents 2,425,755, 2,425,845 and 2,774,733 such as Ucon -50HB170, Ucon 50HB660 or Ucon LB550X and which are copolymerts of ethylene and 1,2-propylene oxides the mono and diols as well as their ether derivatives; organic esters of an aliphatic dibasic acid such as di-Z-ethyl hexyl sebacate or di-Z-ethyl hexyl adipate and the like. The hydrocarbon oils may be blended with fixed oils such as castor oil, lard oil and the like and/ or 30v synthetic oils as mentioned or silicone polymers and the like.- Typical oils of this type are petroleum motor oils (A) which is paraffinic in character and (B) which is naphthenic in character having the following properties:

I Other suitable oils are the gas turbine lube oils having the following properties:

Gr e 1010 1065 Flash, 000, F 300 465 Pour, F 10 0 Viscosity, SUS at F 59. 4 630 Neutral N umber 0. 02 0. 01 Ash None None The following compositions are illustrative of the invention; the percentages being by weight.

Composition A: Percent Example I additive 2 Q1010 mineral oil Balance Composition B:

Example I additive 2 Glycerol monooleate 2 1010 mineral oil Balance Composition C:

Example HI additive 2 Glycerol monooleate 8 1010 mineral oil Balance Composition D:

Example IV additive 2 5 Glycerol monooleate 5 1010 mineral oil Balance Composition E:

Example H additive 1010 mineral oil Balance Composition F; a v

Example V additive 2 C H OH (made by 0x0 process) 3.5 v l010minera1 oil -.Ba1au,ce

Composition G:

Example I additive 2 Laurie acid 2 SAE'90 mineral oil Balance Composition H:

Example -I additive 2 c n on .(made .by Oxo process) a 2.74 SAE 90 mineral oil Balance Composition I:

Example I additive Ucon 50HB660 (polyethylene-propylene glycol having a SUS at 100 F. of 660) Balance Composition J:

Example I additive 2 Di-Z-ethylhexyl sebacate Balance Compositions of this invention were evaluated for their extreme pressure properties on a Spur-Gear machine. The machine consists essentially of two geometrically similar pairs of gears connected by two parallel shafts. The gear pairs are placed in separate gear boxes, which also contain the supporting ball bearings. One of the shafts consists of two sections connected by a coupling. Loading is accomplished by locking one side of the coupling and applying torque to the other. The conditions of the test were:

Speed r.p.m. 3200 and 10,000 Oil temperature F 100 Oil flow-rat cc /sec Load in increments 5 min. at each setting.

Results of the evaluations are given in Table I. For purpose of comparison, the results obtained from the use of the base oil alone, and with other dicarboxylic acids, are also given in Table II.

1010 Mineral 0114-27,, thio alpha,alpha-bls- 3,500 (3,200r1 1mbI (stearic acid).

l0l0glineral oil+2% dodecyl-mercaptosuceim'c 1,400 (10,000 r.p.m.).

aci

IOIOVIiner-al oil+2% heptylmercaptosuccinic 4,200 (3,200 r.p.m.).

aci

1010ldMineral oi1+2% alpha-mercaptobenzoic 4,200 (3,200 r.p.m.).

1010 Mineral oil+l0% glycerol monooleate 1,800 (3,200 r.p.m.). 1010 Mineral 0il+13.25% lauric acid 3,400 (3,200 r.p.m.).

1010 Mju)1eral oi1+2% 0131111011 (oxo' soo(a,20o r.p.m.).

process 1010 Mineral oil 600 (3,200 r.p.m.).

The data show the outstanding enhancement of the load-carrying ability of the oil effected by the mercaptocontaining acids of the invention, as represented by those of Compositions A through F. On the other hand, malonic acid, succinic acid, 3-hexadecyl adipic acid and C -alkenyl succinic acid as well as sulfur-containing acid outside the scope used by applicants such as thiodiglycolic acid, thio-alpha,alpha'bis(stearic acid), dodecylmercaptosuccinic acid, heptylmercaptosuccinic acid, alpha-mercaptobenzoic acid, glycerolmonooleate, lauric acid or Oxo" alcohol effected only a slight improvement.

The sulfur-containing acids of this invention are useful also for providing superior load-carrying properties in lubricating oils which contain minor amounts of other agents which are non-reactive with the dicarboxylic acids, such as silicone anti-foaming agents, alkylphenol antioxidants, polyacrylate ester viscosity-index improvers, and the like.

We claim as our invention:

1. A lubricating oil composition comprising a major 75 amount of mineral lubricating oil and from about 1% to 5% of a sulfur-containing carboxylic acid having the formula S-(CHah-COOR wherein R is an 'oil-solubilizing alkyl radical having from 8 to carbon atoms, R is selected from the group consisting of hydrogen and a C -C alkyl radical, Y is an oxygen-containing radical selected from the group consisting of OH and COOX where X is selected from the group consisting of hydrogen and a hydrocarbyl radical, m is an integer of from 7 to 10 and n is an integer of from 1 to 4, one of the oxygen-containing groups being a carboxy radical.

2. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to 5% of a carboxy C alkyl mercapto-substituted long chain fatty acid, said carboxy C alkyl mercapto radical being from 7 to 10 carbon atoms away from the carboxyl radical of the fatty acid.

3. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to 5% of a carboxy C alkyl mercapto-substituted long chain fatty alcohol, said carboxy C alkyl mercapto radical being from 7 to 10 carbon atoms away from the hydroxyl radical of the fatty alcohol.

4. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to 5% of a carboxy C alkyl mercapto-substituted ester of a long chain fatty acid, said carboxy C alkyl mercapto radical being from 7 to 10 carbon atoms away from the ester group.

5. A mineral lubricating oil composition comprising a major amount of mineral lubrication oil and from about 1% to 5% of a carboxy methyl mercapto-substituted long chain fatty acid, said methyl mercapto radical being from 7 to 10 carbon atoms away from the carboxyl radical of the fatty acid.

6. The lubricating oil composition of claim 1 containing from about 0.1% to about 10% of an oil-soluble monoester of a fatty acid having 1030 carbon atoms and a glycerol.

7. The lubricating oil composition of a claim 1 containing from about 0.1% to about 10% of an oil-soluble branched-chain OX0 alcohol.

8. The lubricating oil composition of claim 1 containing from about 0.1% to about 10% of an oil-soluble long-chain fatty acid having '10-30 carbon atoms.

9. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 11% to 5% of 9- and 10-carboxymethylmercaptostearic acid.

10. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to about 5% of 9- and 10-carboxymethylmercapto-Z-hydroxystearic acid.

11. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to about 5% of glyceryl tris(9- and l0-carboxymercaptostearate.

13. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and. from about 1% to about 5% of 9- and lO-carboxymethylmercaptostearyl alcohol.

14. The lubricating oil composition of claim 9 containing from about 0.1% to about 10% of glycerol monooleate.

15. The lubricating oil composition of claim 9 containing from about 0.1% to about 10% of lauric acid.

16. The lubricating oil composition of claim 9 containing from about 0.1% to about 10% of an oil-soluble branched-chain 0x0 alcohol.

17. The lubricating oil composition of claim 9 containing from about 0. 1% to about 10% of glycerol 7 monooleate.

18. The lubricating composition of claim 12 containing from about 0.1% to about 10% of an oil-soluble branched-chain 0x0 alcohol.

Refcrences Cited in the file of thispatent f P ED AT PATENT ,1

Burwell et a1. Apr; 27, 1943 Gresham ct al Sept. 28, 1948 Perry Jan. 18, 1949 Rudel etal. July 7, 1953 Mulvaney Mar. 6, 1956 

1. A LUBRICATING OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF MINERAL LUBRICATING OIL AND FROM ABOUT 1% TO 5% OF A SULFUR-CONTAINING CARBOXYLIC ACID HAVING THE FORMULA 